pystackflame

Generate flamecharts from Python stacktraces in logs

pystackflame is a command-line tool that parses Python logs for stack traces and turns them into flamecharts or weighed graphs for performance analysis, visualization, and debugging.

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Features

• Generate FlameGraph-compatible output
• Build weighted execution graphs from logs and saves them in json format.
• Python 3.14+ support
• Fast and lightweight CLI built with click
• Developer-friendly with optional linting via ruff

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Installation

We recommend using uv for fast dependency management:

uv sync -p 3.14
source .venv/bin/activate
pystackflame --help

Possible applications

Web Service Error Hotspots

Aggregate Python exceptions in your web server (e.g. Flask/FastAPI/Django) logs to quickly pinpoint which request-handling paths are failing most often without any need of restarting your application.

pystackflame flame /var/log/myapp/**/*.log -o web_errors.flame

Analysis of the historical data

Identify problematic places in the codebase that require the most attention.

pystackflame flame /var/log/all_logs_we_have/**/*.log -o errors.flame
./flamegraph.pl errors.flame > example.svg

Performance Regression Detection in CI

As part of your GitHub Actions or GitLab CI pipeline, run against the previous and current test logs to compare flamecharts—spot new slow-paths introduced by recent commits.

pystackflame flame old_tests.log -o baseline.flame
pystackflame flame new_tests.log -o current.flame

Visualize of diff the two SVGs or flame files to analyze regressions

Batch-Job Profiling

For long-running data-processing jobs (ETL, ML training, batch analytics), collect stacktraces on failure or periodically dump traces, then visualize the cumulative “hot” stacks to optimize slow stages.

pystackflame flame /logs/batch_job_*.log -o batch_profile.flame

Chaos-Engineering Fault Analysis

During fault-injection experiments, collect and compare flamecharts from healthy vs. faulted runs to understand how injected errors propagate.

pystackflame flame healthy.log -o healthy.flame
pystackflame flame chaos.log   -o chaos.flame

Advanced filtering

You can specify an option --trace-filter / -tf [PATH_PREFIX] to filter tracebacks to include only those paths that start with the given prefix and filter out the prefix out from the output. This is useful to restrict the flamechart or graph output to only relevant code paths with relevant names.

Additionally, you can specify multiple --exclude / -e [PATH_PREFIX] to exclude traces that starts from the given path prefix. Wildcard is supported as well.

Example

This command

pystackflame flame ~/test.log -tf '/opt/app/venv/lib64/python3.9/site-packages' 

Will produce the following flame data output

package;database;session.py;wrapper 2
package;apihelper.py;_make_request 2
package;apihelper.py;_check_result 2

And this command

pystackflame flame ~/test.log

Will give you this

/;opt;app;venv;lib64;python3.9;site-packages;package;database;session.py;wrapper 2
/;opt;app;venv;lib64;python3.9;site-packages;package;apihelper.py;_make_request 2
/;opt;app;venv;lib64;python3.9;site-packages;package;apihelper.py;_check_result 2

However, this command

pystackflame flame ~/test.log -tf '/opt/app/venv/lib64/python3.9/site-packages/package/apihelper.py' 

Will produce the following output

_make_request 2
_check_result 2

Usage

• The filter must start with / (absolute path).
• * can be used to match any folder (e.g., /var/log/app-logs/dates/*/application).
• The filter must not end with /.

Result:

• Only stack trace frames that match the filter will be added to the flamechart or graph.
• Useful for narrowing down logs to project-specific code or a specific dependency tree.